Ok.
Warning!
I have no experince with code, and I only have basic electronics knowledge, but have built DIY kits in the past and can follow signal flow in a schematic, and can tell a resistor from a pot/transistor etc.

So I have been toying with an idea.
I have an analog device, that does not have memory, but I would love it to have memory:)

Could I use an arduino with a shield to control it?

I want something like this:

Analog device control pot (pot/switch etc) send to arduino, and then to analog device circuit board.
The arduno would be in between.

My idea would be to take a specific pot on the device, and note its ohm value (seems like all pots are 110k lin), and then emulate that on the arduino.
I would then desolder the pot and in its place, would place a pot that is not connected to the device, but goes directly a arduino in port on a shield (or similar). Then the arduino would control a digital pot (or whatever) that is connected to the solder points where the original pot was soldered in.

So basically I want the arduino to function as a digital pot. (many pots and switches actually, about 53 total).
I *DONT* want to digitize any of the devices analog signals. I only want to control them.
What specific shield could be used?
Is the digital pot the most elegant and easy/cheap solution?
Could you point me in the right direction post some links etc, pretty please:)

This is my findings so far:

I looked at the schematic of my device, and sometimes the pots are connected to +15v and other times -5.
I couldnt seem to find a single digital pot that covered from -5 to +15. I guess I would need different pots (some +15 in specific places, and some -5 in other places?). Or maybe it doesnt matter, since the whole +15/-5 i just a matter of polarity?

It has a supply voltage of 1,8 to 36 volts.
It also has 256 steps, which is ok. Not amazing, better than normal midi, which has 127 steps.

Would this pot work in cases where it is connected to +15v and -5v?
It doesnt have to go from +15 to-5 in the same connection. The -5 is one pot, the +15v is another pot.

If this could be used, I guess I would move on to the whole coding and hardware aspect.
Since i want to connect about 54 pots/switches to the arduino, what shield should i use?
I'm thinking that i can get around with this, by doing some multiplexing, and not be needing physically 54 inputs?

And then there is the coding part!!! what am i thinking! I know nothing about it!
Heheh:)
I'm trying to find out the cheapest way to get this done, and to see if it makes sens to do at all. It is a hobby project, so i dont mind learning lots of new stuff by doing this.

The system can be implemented as dual
rail (±18V) relative to the digital logic ground (DGND).

So it must be possible to cover your needs in the +15 to -5 volt region.
But before you buy a humungus amount of digital potmeters and to keep you from a huge disappointment I think it is a good idea to just buy 2 of these potmeters (or maybe 4 because you can have 4 individual potmeters to one I2C bus ), wire them up, program your arduino or whatever processor you will be using, and get a feeling for what they can handle qua voltages, what is the speed, the cross talk all that kind of things.
And when you feel comfortable about it all, you can expand, buy more pots, go ahead multiplexing the sh*t out of it, and if you feel like it ask more questions as you progress in the diy world.
Good luck!_________________ my synth

Oh, btw: If you do want to have that much potentiometers like you stated in your first post, try to find SPI controlled pots, because they are easier to multiplex and faster than I2C ones._________________ my synth

I never work with shields so I don’t know. I usually buy a arduino nano or something similar, solder that on a perfboard and add electronic parts that I need for the module I’m working on.
See below for some youtubes of my synth. Almost every module I made has an arduino in it.
About the filtering: If you use these digital pots to control a voltage, some filtering may be benificial but a good start is also to make smaller steps in a short time so you already have kind of a ramp, so the filtering can be less heavy.
If you use the digital pots as a volume control there is no need to filter, it even could destroy your signal this way._________________ my synth

I'll have to go without SPI it seems (i'll probably get the one I linked to earlier).

And i'm planning on buying the behringer pro one (i'm sure you are familiar with it), and add this once I gets released.

Here is a schem:

Actually, its of the original, but i'm assuming it will be very close to the original in every way.

I have messed around with the model D already and it's a great sounding machine. I really like what Behringer is doing, but I would really like memory on these little things. (I had a modular as well, a formant elektor DIY synth+many other classic mono/polysynths, but have sold them all over time).

Let me know if you have any thoughts on the project/schematic. Anything I should be aware of etc.

And if you could point me to anything about coding, then it would be much appreciated.

I'll probably get back once i get the synth or when i find new problems.

I only had a quick glance at the schematic but it looks like you won't need the range for the pots you might think you need.
For example the "AMP SUSTAIN" pot (R1204) is connected in series with a resistor to +15V. since this pot is 100K and the
resistor is 200K the voltage over the pot itself is only 5V. Also a lot of pots could probably be replaced with DACs since they
just provide a (DC) voltage, but if I understand correctly that's something you don't want to do.

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